module top_module (
    input [3:0] x,
    input [3:0] y, 
    output [4:0] sum);

    wire	[2:0]	cout;
    
    assign {cout[0], sum[0]} = x[0] + y[0];
    assign {cout[1], sum[1]} = cout[0] + x[1] + y[1];
    assign {cout[2], sum[2]} = cout[1] + x[2] + y[2];
    assign {sum[4], sum[3]} = cout[2] + x[3] + y[3];
    
endmodule
